Many devices have been developed for printing or generating images on a medium. Some such devices, inkjet printers for example, operate by selectively ejecting ink onto the print medium to form the desired image. Other devices, such as laser printers, form an image using toner on an imaging drum and then transfer the image to a print medium. Photographic processes allow light to cause a chemical change in photographic film to capture an image.
A relatively new thermally sensitive process is known as thermo-autochrome printing. Thermo-autochrome printing is more akin to photography than printing, and has emerged recently in printers marketed as companion devices for use with a digital camera.
Thermo-autochrome paper contains three color-forming layers—cyan, magenta and yellow—that each include components that are released and combined by heat to form a dye or pigment of a desired color. In other words, each color-forming layer is sensitive to a particular temperature and displays its corresponding color when heated to that temperature. Of these colorants, yellow has the lowest temperature sensitivity, then magenta, followed by cyan. Specific portions of the color-forming layer can be heated to create the corresponding color in only the heated areas.
A typical thermo-autochrome printer is equipped with a thermal head that selectively heats portions of the paper to activate the dye or pigment. The thermal head typically has heating resistors that are brought into close thermal contact with the thermo-autochrome paper to selectively heat the temperature-sensitive layers.